Answer:
Two major subdivisions of the Precambrian era are Archean and Proterozoic.
Explanation:
The whole period of earth before the formation of the oldest rocks is known as the Precambrian period. It comprises all geological time before 600 million years ago. The two major subdivisions of the Precambrian period are-
1. Archean - It is an older subdivision of the Precambrian period prior to 2500 million years ago. It can be divided into early, middle and late.
Most abundant fossils are found during this period. In this period microfossils of photosynthesizing bacteria known are found.
2. Proterozoic- It is the second major subdivision of the Precambrian period prior to 600 million years ago up to 2500 million years ago. Traces of the Edicara fauna, bacteria, and blue-green algae and first oxygen dependent life-form are found in the Proterozoic period.
